Hydraulic circuits may include a pressure responsive flow source for powering a hydraulic load. The load may include an accumulator for storing energy.
The pressure responsive flow source may be any variable output flow source whose output is controlled by a pressure signal. Examples include but are not limited to variable displacement pumps and fixed displacement pumps with valves to increase and decrease flow from the fixed displacement pump.
The accumulator may be any device that stores energy in the form of fluid pressure. Examples include but are not limited to bladder type accumulators that store fluid under pressure in an expandable elastomeric chamber and piston type accumulators that store fluid under pressure in a cylinder that includes a piston acting against the fluid.
The accumulator may operate between a lower pressure setting and a higher pressure setting. When the accumulator is at its lower pressure setting, it is desirable to provide a signal to the pressure responsive flow source to increase fluid flow to recharge the accumulator. When the accumulator reaches its upper pressure setting, it is desirable to provide a signal to the pressure responsive flow source to decrease fluid flow to the accumulator. It is common to use an unloader valve that is responsive to accumulator pressure to supply a control signal to a load sensing device, such as a pump or valve, for controlling the supply of fluid to the accumulator.